Conservation Bio Quiz 3

What are the methods for predicting population trends and risk of extinction

estimates of population size

predictions about trend in population

predictions about variability over time

What model performs the same way for a given set of initial conditions

deterministic

>

=

<

Which models can give a range of outcomes from the same initial conditions?

stochastic

stochastic model graph

When are the effects of stochasticity and randomness most important?

when studying small population, and making short to medium term predictions

Most population viability analyses will include

some form of stochasticity

environmental stochasticity

temporal variation in vital rates drive by changes in the biotic or abiotic environment

Populations experiencing good and bad years can end up having a (smaller or larger) - population size than one experiencing a constant average growth rate

smaller

T or F: bad growth years have a large influence on population size / growth

T

stochasticity is

random population distribution

Adding stochasticity to population growth generally does what to the predicted long-term population size

lowers it

What population sizes does environmental stochasticity affect the growth rate of?

any

What sized populations are often more at risk for environmental stochasticity?

local or small

Models with no stochasticity predict a

population size

Models with stochasticity predict a

distribution of population sizes

Two populations each start at 1,000 and have

the same average one-year lambda of 1.0.

Population A: λ = 1.0 every year.

Population B: λ alternates between 0.5 and 1.5.

After 10 years, which population is larger?

A

More stochasticity predicts - populations

lower

catastrophes

hard to predict or model but ultimately may be a common contributor to extinction

In order to be resilient to catastrophe what populations are necessary

multiple viable ones

The heath hen could have avoid extinction if

there was spatial variation in the environment

Demographic stochasticity

extinction may occur due to order of births and deaths

When is demographic stochasticity important

when the population is so small that you can’t get away with rounding your predictions

Consider population in which 1 female has

50% probability of producing 1 female offspring in summer

30% probability of dying the following winter

what is the probability of extinction over this year?

A. 0%

B. 10%

C. 15%

D. 30%

E. 50%

C

50% probability of producing 1 female offspring

30% probability of dying every year.

Best case scenario is she survives and has a daughter,

now N = 2

Probability both die

0.09

50% probability of producing 1 female offspring

30% probability of dying every year.

Best case scenario is she survives and has a daughter,

now N = 2

Probability both do not breed

0.25

50% probability of producing 1 female offspring

30% probability of dying every year.

Best case scenario is she survives and has a daughter,

now N = 2

Probability both die = 0.3*0.3 = 0.09

Probability both do not breed = 0.5*0.5 = 0.25

So probability of extinction next year=

2.25%

Conservation genetics

application of genetic techniques to conservation problems

describing and preserving genetic diveristy

Techniques in conservation genetics

• get DNA from some fraction (or all) individuals

• sequence some portion of the genome

• Infer statistics based on these loci (traditional approach)

• genomics becoming increasingly important

What is the traditional approach in conservation genetics

infer statistics based on loci

Polymorphism

• allelic diversity

• fraction of gene loci in which alternative alleles of a gene occur in a population.

Population heterozygosity

proportion of gene loci at which the average individuals in the population is heterozygous

What does bein heterozygous mean

an individual carries two different alleles at this locus

As alleles are lost, polymorphism is going - and population heterozygosity -

down, goes down

Which individuals do better (in terms of genetic diversity)

individuals with more diverse genomes

Populations with higher heterozygosity often have higher

fitness

H=

fraction of heterozygosity remaining after one generation

genetic drift

random fluctuations of gene frequencies over time due to chance alone

H t = H^t

H t = heterozygosity at end of period

H = heterozygosity at beginning of period (H00)

t = length of period

If H near 1

diversity is being conserved

If H is well below 1

diversity is being lost

Based on this equation, as the

effective population size gets larger what happens to

the rate at which diversity is lost through genetic drift?

A. The rate of loss goes up

B. The rate of loss goes down

C. The rate of loss stays the same

B

The rate of loss goes down as effective population size

goes up

Drift can be very high in what sized populations?

small

10

100

Heterozygosity decreases much faster for what populations?

small

Effective population size (Ne)

population size relevant for determining genetic effects or the number of individuals contributing genes to the next generation.

What is Ne typically between - of N

0.1 and 0.5

o²= and k =

variance in number of progeny among females

average number of progeny

as the variance in the number of progeny (o²) increases, Ne -

decreases

Nm = and Nf =

number of breeding males, number of breeding females

The effective population size - (increases or decreases) when the number of males and females in a breeding population of individuals is increasingly unequal

decreases

Ni=

number in population at time t